const MayBe = require('folktale/maybe')

const toRMB = v => MayBe.fromNullable(v)
  .map(v => v.replace('$', ''))
  .map(parseFloat)
  .map(v => v * 7)
  .map(v => v.toFixed(2))
  .map(v => '￥' + v)
  .getOrElse('noting')
  
console.log(toRMB(null))
